[PATCH v4 0/4] PCI: Add DOE support for endpoint

[Aksh Garg <a-garg7@ti.com>]

This patch series introduces the framework for supporting the Data
Object Exchange (DOE) feature for PCIe endpoint devices. Please refer
to the documentation added in patch 4 for details on the feature and
implementation architecture.

The implementation provides a common framework for all PCIe endpoint
controllers, not specific to any particular SoC vendor.

The changes since v1 are documented in the respective patch descriptions.

v3: https://lore.kernel.org/all/20260427051725.223704-1-a-garg7@ti.com/
v2: https://lore.kernel.org/all/20260401073022.215805-1-a-garg7@ti.com/
v1 (RFC): https://lore.kernel.org/all/20260213123603.420941-1-a-garg7@ti.com/

Below is a code demonstration showing the integration of DOE-EP APIs with
EPC drivers.

Note: The provided code is just to show how an EPC driver is expected to
      utilize the pci_ep_doe_process_request() and pci_ep_doe_abort() APIs,
      and might not cover all the corner cases. The below implementation
      also expects the EPC hardware to have some memory buffer to store the
      data from(for) write_mailbox(read_mailbox) DOE capability registers.

============================================================================

/* ========== DOE Completion Callback (invoked by DOE-EP core) ========== */

static void doe_completion_cb(struct pci_epc *epc, u8 func_no, u16 cap_offset,
			       int status, u16 vendor, u8 type,
			       void *response_pl, size_t response_pl_sz)
{
	struct epc_driver *drv = epc_get_drvdata(epc);
	u32 *response = (u32 *)response_pl;
	u32 header1, header2;
	int payload_dw, i;

	if (status < 0) {
		/* Error: set ERROR bit in DOE Status register */
		writel(1 << DOE_STATUS_ERROR,
		       drv->base + PF_DOE_STATUS_REG(func_no, cap_offset));
		goto free;
	}

	if (readl(drv->base + PF_DOE_CTRL_REG(func_no, cap_offset)) & DOE_CTRL_ABORT) {
		/* Aborted: do not send response */
		goto free;
	}

	/* Success: write DOE headers first, then response to the read memory */

	/* Header 1: Vendor ID (bits 15:0) | Type (bits 23:16) */
	header1 = (type << 16) | vendor;
	writel(header1, drv->base + PF_DOE_RD_MEMORY_WR_REG(func_no, cap_offset));

	/* Header 2: Length in DW (including 2 DW of headers + payload) */
	payload_dw = DIV_ROUND_UP(response_pl_sz, sizeof(u32));
	header2 = 2 + payload_dw;  /* 2 header DWs + payload */
	writel(header2, drv->base + PF_DOE_RD_MEMORY_WR_REG(func_no, cap_offset));
	
	/* Set READY bit to signal response ready */
	writel(1 << DOE_STATUS_READY,
	       drv->base + PF_DOE_STATUS_REG(func_no, cap_offset));

	/* Write response payload DWORDs to Read memory */
	for (i = 0; i < payload_dw; i++)
		writel(response[i],
		       drv->base + PF_DOE_RD_MEMORY_WR_REG(func_no, cap_offset));

	/* Wait for the memory to empty before clearing the READY bit */
	while (!RD_MEMORY_EMPTY()) {/* wait */}

	writel(0 << DOE_STATUS_READY,
	       drv->base + PF_DOE_STATUS_REG(func_no, cap_offset));
	
	/* unset BUSY bit */
	writel(0 << DOE_STATUS_BUSY,
	       drv->base + PF_DOE_STATUS_REG(func_no, cap_offset));
free:
	kfree(response_pl);
}

/* ========== DOE Interrupt Handler (triggered on GO bit from root complex) ========== */

static irqreturn_t doe_interrupt_handler(int irq, void *priv)
{
	struct epc_driver *drv = priv;
	u16 cap_offset = extract_cap_offset_from_irq(irq);
	u8 func_no = extract_func_from_irq(irq);
	u32 header1, header2, length_dw, *request;
	u16 vendor;
	u8 type;
	int i, ret;

	/* Read first header DWORD: Vendor ID (bits 15:0) | Type (bits 23:16) */
	header1 = readl(drv->base + PF_DOE_WR_MEMORY_RD_REG(func_no, cap_offset));
	vendor = header1 & 0xFFFF;
	type = (header1 >> 16) & 0xFF;

	/* Read second header DWORD: Length in DW (includes 2 DW of headers) */
	header2 = readl(drv->base + PF_DOE_WR_MEMORY_RD_REG(func_no, cap_offset));
	length_dw = header2 & 0x3FFFF;  /* Bits 17:0 */

	if (!length_dw)
		length_dw = PCI_DOE_MAX_LENGTH;

	length_dw -= 2;  /* Subtract 2 DW of headers to get payload length */
	/* Allocate buffer for complete request (headers + payload) */
	request = kzalloc(length_dw * sizeof(u32), GFP_ATOMIC);
	if (!request) {
		writel(1 << DOE_STATUS_ERROR,
		       drv->base + PF_DOE_STATUS_REG(func_no, cap_offset));
		return IRQ_HANDLED;
	}

	/* Read remaining payload DWORDs from Write memory */
	for (i = 0; i < length_dw; i++) {
		while (WR_MEMORY_EMPTY()) { /* wait */ }
		request[i] = readl(drv->base + PF_DOE_WR_MEMORY_RD_REG(func_no, cap_offset));
	}
	/* Set BUSY bit */
	writel(1 << DOE_STATUS_BUSY,
	       drv->base + PF_DOE_STATUS_REG(func_no, cap_offset));

	/* Hand off to DOE-EP core for asynchronous processing */
	ret = pci_ep_doe_process_request(drv->epc, func_no, cap_offset,
					 vendor, type, (void *)request,
					 length_dw * sizeof(u32),
					 doe_completion_cb);
	if (ret) {
		writel(1 << DOE_STATUS_ERROR,
		       drv->base + PF_DOE_STATUS_REG(func_no, cap_offset));
		kfree(request);
	}

	return IRQ_HANDLED;
}

/* ========== Abort Handler (triggered on ABORT bit from root complex) ========== */

static irqreturn_t doe_abort_handler(int irq, void *priv)
{
	struct epc_driver *drv = priv;
	u16 cap_offset = extract_cap_offset_from_irq(irq);
	u8 func_no = extract_func_from_irq(irq);

	/* Abort pending/in-flight operations in DOE-EP core */
	pci_ep_doe_abort(drv->epc, func_no, cap_offset);

	/* Discard Write memory contents */
	writel(DOE_WR_MEMORY_CTRL_DISCARD,
	       drv->base + PF_DOE_WR_MEMORY_CTRL_REG(func_no, cap_offset));

	/* Clear status bits */
	writel((0 << DOE_STATUS_ERROR) | (0 << DOE_STATUS_BUSY) |
	       (0 << DOE_STATUS_READY),
	       drv->base + PF_DOE_STATUS_REG(func_no, cap_offset));

	return IRQ_HANDLED;
}

====================================================================================

Aksh Garg (4):
  PCI/DOE: Move common definitions to the header file
  PCI: endpoint: Add DOE mailbox support for endpoint functions
  PCI: endpoint: Add support for DOE initialization and setup in EPC
    core
  Documentation: PCI: Add documentation for DOE endpoint support

 Documentation/PCI/endpoint/index.rst          |   1 +
 .../PCI/endpoint/pci-endpoint-doe.rst         | 329 +++++++++++
 drivers/pci/doe.c                             |  11 -
 drivers/pci/endpoint/Kconfig                  |  14 +
 drivers/pci/endpoint/Makefile                 |   1 +
 drivers/pci/endpoint/pci-ep-doe.c             | 553 ++++++++++++++++++
 drivers/pci/endpoint/pci-epc-core.c           |  92 +++
 drivers/pci/pci.h                             |  48 ++
 include/linux/pci-doe.h                       |   8 +
 include/linux/pci-epc.h                       |   9 +
 10 files changed, 1055 insertions(+), 11 deletions(-)
 create mode 100644 Documentation/PCI/endpoint/pci-endpoint-doe.rst
 create mode 100644 drivers/pci/endpoint/pci-ep-doe.c

-- 
2.34.1